Organoids are in vitro-cultured three-dimensional structures that recapitulate key aspects of in vivo organs. They can be established from pluripotent stem cells and from adult stem cells, the latter being the subject of this review. Organoids derived from adult stem cells exploit the tissue regeneration process that is driven by these cells, and they can be established directly from the healthy or diseased epithelium of many organs. Organoids are amenable to any experimental approach that has been developed for cell lines. Applications in experimental biology involve the modeling of tissue physiology and disease, including malignant, hereditary, and infectious diseases. Biobanks of patient-derived tumor organoids are used in drug development research, and they hold promise for developing personalized and regenerative medicine. In this review, we discuss the applications of adult stem cell-derived organoids in the laboratory and the clinic.